What happens if you wind a coil around an iron core, stop, centre tap it, then wind the same amount of turns around (the first coi) again? (you end up with a coil within a coil)

I'm particularly interested in what the inductance would be for each half.

For example I know that..... 100 turns of 0.3mm wire yields about 0.8mH

so for this particular coil scenario, I end up with ....

100 turns of 0.3mm wire = 0.8mH

ground tap

100 turns of 0.3mm wire = 0.8mH

if putting an AC signal through one half of the coil will it affect the other half? (yes I know each leg will require an inverted signal...but I'm wondering if the AC signal through one coil impacts the other, therefore playing havoc with the inductance aspect)